• DIC — partial activation of clotting factors and destruction of stored cells, either in old blood or when transfusion is incompatible.

• Anaphylactoid reaction — urticaria is common and probably due to a reaction to transfused plasma proteins; if severe it may be treated by slowing the transfusion and giving chlorpheniramine 10mg IV/IM. In severe anaphylaxis, in addition to standard treatment, the transfusion should be stopped and saved for later analysis and a sample taken for further cross-matching.